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Full text of "Practical Organic Chemistry"

MONOBROMACETIC ACID

PREPARATION 18.
Monobromacetic Acid, CH2Br.COOH.

Hell,  Bcr.)   1881,   14,   891 ;   Volhard,   Annalen,  1887,  242,
141 ; Zelinsky, Ber., 1887, 20, 2026.

30 grms. (30 c.c.) glacial acetic acid.
I05     3)      (35 c.c.) bromine.
5            red phosphorus.

All the above substances must be dry. The acetic acid is frozen in
ice, and any liquid drained off, and the red phosphorus is washed
with water to free it from phosphoric acid, dried in the steam oven,
and kept over sulphuric acid in a desiccator until required. The
bromine is placed in a separating funnel with half its volume of
concentrated sulphuric acid overnight, and
then separated. The apparatus is shown in
Fig- 63 . It consists of a round flask (250 c.c.)
attached to an upright condenser, which is
provided with a cork. A tap-funnel con-
taining the bromine passes through one
hole, and a wide bent tube, attached at its
lower end to a funnel, passes through the other.

As a large quantity of hydrobromic acid is

evolved in the reaction, the funnel is made to

touch   the  surface  of water  contained  in a

beaker,   whereby  it  is completely  absorbed.

The phosphorus and acetic acid are placed

in the flask, and bromine dropped in from the

tap-funnel.*    A vigorous reaction occurs, and

the  liquid becomes  very  warm.    After half

the   bromine    has   been   added   the   action

moderates, and the remainder may be run in

more  quickly.    When  the  whole   has  been

added,   the   liquid  is  boiled   gently until  the  colour  of the

bromine   disappears.     It   is  now   allowed   to  cool,   and the

liquid decanted into a distilling flask for distillation in vacua.

Care must be taken not to touch the substance with the hands,

as even a small quantity produces very unpleasant sores.    The

apparatus for distilling in vacua is shown in Fig. 56 (p. 85).

FIG. 63.